1. Field of the Invention
The present invention relates to restaurant equipment, more particularly, to manual presses for producing flat sheets of dough.
2. Description of the Related Art
The purpose of a dough press is to flatten a quantity of dough to produce, for example, a pizza crust. A typical manual dough press has two horizontal platens with opposing working surfaces. Normally, the surfaces are flat, except when special shapes are desired, for example, to create a raised crust on a pizza. The lower platen is fixed vertically, but is typically designed to swing out from the press so that dough can be removed from or placed on the working surface. The upper platen is attached to a mechanism that moves the upper platen vertically, while remaining aligned and parallel with the lower platen. The mechanism is manually operated by a handle that extends from the front of the press. Raising and lowering the handle respectively raises and lowers the platen. In use, the lower platen is pivoted out from the press, a quantity of unformed dough is placed on the lower platen, and the lower platen is returned to its operative position. The operator lowers the handle, putting enough pressure on the handle to flatten and shape the dough as desired. Optionally, the dough press may contain a stop whereby the upper platen's range of travel is limited. Optionally, one or both platens incorporate heaters for warming the dough to make it more amenable to being shaped. After the dough is pressed to the desired shape, the handle is raised, the lower platen is swung out from the press and the now-shaped dough is removed.
FIG. 2 illustrates two aspects of the platen-lowering mechanism of manual dough presses of the prior art. The upper platen 200 is attached to a shaft 202 that reciprocates within a cylinder 204 so that the platens remain aligned and parallel during operation. The shaft is driven manually by a rack and pinion, where the rack 206 is mounted vertically to the shaft 202. The rack 206 travels vertically through a slot 208 in the cylinder wall. The pinion 210 is attached to an axle 214 that is a portion of the handle 212. As the handle 212 is moved up or down, the pinion 210 rotates, causing the shaft 202 to reciprocate within the cylinder 204. In order to retain the upper platen in the position desired by the operator, a counterbalance mechanism is employed. A collar 216 is tightened around the axle portion 214 of the handle 212 to which the pinion 210 is attached. This has the effect of providing enough friction to overcome the weight of the platen 200 and shaft 202 to hold the platen 200 in the vertical position desired by the operator.
There are several shortcomings to this design. The shaft/cylinder combination must be lubricated on a regular basis in order to work smoothly and not bind. With the shaft 202 attached directly to the upper platen 200, lubricant slides or is pushed down the shaft 202 and can end up on the platen 200. Because the working surface of the platen 200 is in contact with the dough being pressed, great care must be taken to make sure that the lubricant does not find its way to the dough press surface of the platen 200, otherwise the surface may become contaminated and, in turn, contaminate the dough. If the shaft/cylinder combination is not lubricated on a regular basis, it may bind and cause breakage of the teeth of the rack 206 and/or the pinion 210.
Regarding the counterbalance mechanism, when raising the platen, the operator must overcome, not only the not insignificant weight of the platen, but the friction of the collar. In addition, the collar must be regularly adjusted as it or the axle wears. If the collar is too tight, the it takes more work by the operator to raise and lower the platen. If the collar is too loose, the platen may fall, creating a safety hazard, such as crushed fingers. Eventually, the collar or handle must be replaced as one or the other wears out. Care must also be taken that lubricant does not contaminate the collar, and thereby reduce its effectiveness.
Some prior art dough presses incorporate a mechanism for maintaining downward pressure on the upper platen without need for the operator to maintain manual pressure on the handle. One such mechanism uses a pneumatic cylinder, but also requires a source of high pressure air with all of the accompanying apparatus, such as a compressor and a storage tank. Another mechanism uses a hydraulic cylinder, but also requires a source of hydraulic fluid. A third mechanism uses a linear electric motor, which requires a source of electric power. All of these prior art mechanisms add cost and complexity to the manual press.